Life cycle water, energy and cost analysis of multiple water harvesting and management measures for apartment buildings in a Mediterranean climate

Local water harvesting, demand reduction and wastewater treatment measures at a building scale can help manage water resources around the Mediterranean. This study conducts a life cycle water, energy and cost analysis of rainwater and condensate water harvesting, water conservation, wastewater treatment and three combinations of these measures over 50 years, using an apartment building in Sehaileh, Lebanon. The measures’ performance is further investigated through a comprehensive sensitivity analysis that extends the applicability of findings. Reducing water demand in the building through efficient water fixtures and appliances can decrease annual water and primary energy use by 1 534 kL and 130 GJ, respectively, while saving 530 USD every year. Wastewater treatment requires 230 MJ and costs 0.97 USD per kL of water saved, necessitating subsidies to be competitive. Rainwater and condensate water harvesting cover 4.8% and 1% of the total demand, respectively, but can reduce infrastructure spending, avoid water leakage and reduce urban run-off. Combining all measures reduces mains water supply by up to 75% for 1 MJ/kL saved and zero life cycle cost. Finally, a metered, seasonal and demand-driven water pricing scheme is recommended to better relate building occupants with the intermittent and scarce nature of water around the Mediterranean.